This disclosure relates to combustion chambers in gas turbine engines. In particular, the invention relates to materials for hot gas path parts, such as, but not limited to, combustion liners within the combustion chambers of gas turbines.
The combustion system of a gas turbine generates hot gases. The hot gases can be utilized to drive a turbine. The turbine, in turn, can drive a compressor, wherein the compressor provides compressed air for combustion in the combustion system. Additionally, the turbine produces usable output power, which can be connected directly to power-consuming machinery or to a generator.
The combustion system for a gas turbine may be configured as a circular array of combustion chambers. The combustion chambers are arranged to receive compressed air from the compressor, inject fuel into the compressed air to create a combustion reaction, and generate hot combustion gases for the turbine. The combustion chambers are generally cylindrically shaped, however other shapes of combustion chambers are possible. Each combustion chamber comprises one or more fuel nozzles, a combustion zone within the combustion liner, a flow sleeve surrounding and radially spaced from the liner, and a gas transition duct between the combustion chamber and turbine.
The combustion zone defines a volume within the combustion liner in which a fuel/air mixture combusts to generate the hot gases. Accordingly, compressed air flows from the compressor to the combustion zone through an annular gap provided between the combustion liner and flow sleeve. Air flowing through this gap can act to cool the outer surface of the liner. The compressor air then can flow into the combustion zone through at least one of the fuel nozzles and holes in the combustion liner. Compressor air can also flow between the liner and flow sleeve in a first direction, can reverse direction as it enters the combustion liner, and can flow as a hot gas out of the liner and combustor, and then into the turbine.
The combustion liner typically operates in a high temperature environment, in which a combustion process generates a stream of high-velocity hot gases that flow through the liner and to the turbine. The combustion liner should be mounted in the flow sleeve to withstand the heat as well, as vibration. Further, the combustion liner should be mounted to withstand loads imposed by the combustion of gases and other forces that act on the combustion chamber.
Large gas turbine combustor components have traditionally been fabricated with superalloys, such as, but not limited to, wrought nickel-based superalloys. As turbine designs evolved for operation at higher temperatures, superior low cycle fatigue, oxidation and creep properties of cast superalloys were desired. Also, multiple cast pieces subsequently were joined to turbine combustor components by metallurgical connecting means, such as but not limited to, brazing or welding. However, these means, such as but not limited to, brazing or welding have not lead to an acceptable outcome since the joint locations did not have the material properties of the remainder of the turbine combustor components. Accordingly, a need for turbine combustor components with connected cast pieces is desired where the connected cast pieces have similar material properties as the turbine combustor components as well as at the means for connecting the connected cast pieces to the turbine combustor components.
Transition pieces have been provided formed from various materials. For example, some transition pieces have been formed with a cast alloy, such as GTD-222, as described in U.S. Pat. No. 6,416,596 granted to Wood et al., and U.S. Pat. No. 6,428,637 granted to Wood et al.). These materials have provided improvement in material properties, such as but not limited to at least one of low cycle fatigue (LCF) resistance and creep strength vs. wrought alloys, manufacturability, machinability, weldability, and oxidation resistance, in turbine combustor components, for example hot gas path parts. These improvements are especially evident with respect to wrought alloy material properties. However, for some high temperature turbine applications, increased material characteristics, such as strength, would provide desirable life potentials. Therefore, there exists a desire to provide turbine combustor components with materials that provides enhanced strength and possible extended turbine life.